It is troublesome to constantly maintain ordinary household knifes in a sharpened condition due to the variations in actual use time of the knife. The user does not always remember to sharpen the knife blade until the knife is so dull that it will not cut efficiently. Often, it is not convenient to hone the knife blade before or after each use, so that over time, the knife blade becomes dull, rendering it difficult to use.
A number of prior art patents have recognized this deficiency with such ordinary knife blades and proposed sharpener sheaths that sharpen the knife blade upon every insertion or withdrawal from the sharpener sheath. Typical patents in this area include U.S. Pat. Nos. 3,774,350 and 4,041,651.
In such prior art sharpener sheaths, the sharpening action has been achieved on each insertion and/or withdrawal of the knife blade to or from the scabbard. The edge of the knife blade engages a fixed sharpening device carried on the scabbard, which is designed to sharpen the blade edge upon each insertion/withdrawal.
Although such sharpener sheaths are effective in sharpening the blade edge, one disadvantage is the sharp edge emerging from the scabbard during, and as part of, the sharpening action. Such an emerging sharp edge may present a risk both to the person withdrawing the knife blade and to objects, such as work surfaces, which are immediately adjacent the emerging blade edge, both of which can be cut by the freshly sharpened edge.
It has further been realized that sharpening the knife blade on every insertion/withdrawal has other disadvantages, the greatest of which is that sharpening may not be required with such frequency. In fact, such frequent sharpening may damage the knife blade, causing excessive wear. The sharpening action causes metal to be removed from the knife blade each time the knife is inserted/withdrawn from the scabbard. Most of the time, specifically after a single use, it is not necessary to sharpen the blade. Hence, these prior art devices can cause excessive wear of the blade.
Yet a further disadvantage of some of the prior art sharpener sheaths is that they fail to provide for safe storage of the knife blade in the sheath or the safe storage of the sheath as a whole. Some of the prior art sharpener sheaths provide a locking device to lock the knife blade in the sheath for storage. However, most of such sharpener sheaths referred to above fail to lock the sharpening device and the blade, so that the sheath, including the blade, may be safely stored.